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Monday, April 24, 2017

1910-1920: The oxygen revolution

Joseph Barcroft (1872-1947)
In 1886 he received his M.D. from Cambridge,
and began his study of hemoglobin.
He exposed himself to different environments
to determine their effects on the human body.
.

Three significant events occurred at the dawn of the 20th century that resulted in increased interest in supplemental oxygen therapy. The first was the invention of a means of measuring oxygen saturation. The second was an experiment that Dr. Joseph Barcroft performed on himself. The third were experiments by WWI physicians to find a treatment for pulmonary edema caused by gas poisoning.

The ability to draw arterial blood was a significant discovery. It was hurter in 1912 who introduced the method. (2, page 693)

Yet even more significant was the machine blood could be inserted into that would determine the how saturated hemoglobin molecules in the blood were with oxygen molecules. This is referred to as oxygen saturation. Once inserted into the machine, the saturation was reported as a percentage.

John Scott Haldane (1850-1936)
He graduated from Edinburgh University in 1884,
and worked with his uncle at Oxford,
where he became interested in air,
its composition, and effects on humans.

Adolf Fick of Germany and Paul Bert of France described oxygen tensions as units of partial pressure, and it was these units that made it possible to describe the difference between arterial and venous blood. Since the partial pressure of oxygen in arterial blood is higher than the partial pressure of oxygen in venous blood. Or at least this is the case in a healthy individual. (1, page 4) (2) (6)

Further studies by various experts determined the normal levels and critical levels of oxygenation. It was determined that a normal arterial saturation of hemoglobin is between 95 and 98 percent, and a normal venous saturation is between 70 and 75 percent. These new values allowed physicians to monitor a patient's oxygenation status, and the effectiveness of oxygenation therapy. (2)(3, page 369)

Among the first to prove the significance of this discovery was Sir Joseph Barcroft, who lived for six days in an atmosphere that had 18 percent oxygen in the air, as opposed to the normal 21 percent that's in roomair. Alvin L. Barach, a pioneer in oxygen therapy, liked to use Barcroft's experiment as an example to prove the significance of oxygenation.

Barach explained:

"On the last day, the oxygen saturation of his arterial blood was 88 per cent., and after the performance of work 83.8 per cent. He lay in the chamber racked with headache, with occasional vomiting, and at times able to see clearly only as an effort of concentration. He became faint on exertion. His pulse, normally 56, had risen to 86. These effects were apparently due purely to oxygen want. The degree of anoxemia that produced them has frequently been found in pneumonia and heart disease by the investigators mentioned above. In many instances, the saturation of the arterial blood falls to far lower levels. It would, therefore, seem likely that lack of oxygen in the degree often found in disease would produce bodily discomfort, disturbances in function and damage to living structure." (3, page 369)

The effects on Barcroft were similar to the effects of pneumonia and heart failure for some patients. Studies showed that the oxygen saturation could range from 75-95 percent in cases of cardiac insufficiency, and 60-95 percent in cases of pneumonia. (2, page 693)

So it became apparent these diseases, as they progress, decrease the amount of oxygen that gets to the blood and to hemoglobin.

Various studies, including the Barcroft study, proved that a low level of oxygen stimulates the central nervous system to stimulate various changes within the body in an attempt to return oxygenation back to normal: heart rate increases, respiratory rate increases in rate but decreases in depth, patient may become delirious and may have hallucinations If not treated, death may result. (2, page 694)

So these studies proved to the medical community the significance of observing the signs and symptoms of poor oxygenation and speedily treating them with oxygen. (2, page 694)

Oxygen was not meant to cure, but to treat the symptom of low oxygenation long enough to allow the physician to remedy the underlying condition, which may include: (2, page 694)

Pneumonia

Acute Cardiac Failure

Severe Hemorrhage

Epidemic Encephalitis

Ascent to high altitudes

Complications of chronic cardiac insufficiency

Pulmonary Edema

Acute Bronchitis

Carbon Monoxide Poisoning

Nitrous Oxide Poisoning

Other anesthesia

Further studies also allowed physicians the opportunity to determine that a therapeutic percent of oxygen for most diseases was between 40 and 60 percent, and it's for this reason the oxygen chamber, oxygen catheter, and nasal cannula generally are not effective for oxygenating patients with severe oxygen deprivation. (2, page 696)

Studies likewise showed greater than 70 percent could cause pneumonia, and did so in rabbits. (3, page 373)

It was probably based on these and similar studies that John Haldane, another pioneer of oxygen therapy, would recommend 41% oxygen administration continuously for patients suffering from anoxemia (Haldane would coin a new term to describe this: hypoxemia). (6) (7) (8)

In fact, it is said Haldane once mused:

Intermittent oxygen therapy is like bringing a drowning man to the surface of the water—occasionally. (7) (8)

Yet even while he and other physicians proved the usefulness of continuous oxygen therapy during WWI, it would take a few more years for it to catch on. (6)

Oxygen mask designed by Haldane in 1917

A third significant event was the gas poisonings that occurred during WWI. Phosgene was used by the enemy on the war front because, when it combines with water in the lungs, it creates hydrochloric acid, which damages lung tissue. If inhaled in high enough doses it may cause pulmonary edema within 6-10 hours, leading to acute respiratory distress syndrome (ARDS). As the illness progresses, the lungs lose their ability to pass oxygen to pulmonary capillaries, therefore causing anoxemia or hypoxemia. (6)

While oxygen was not thought to cure these patients, it was believed that it would treat the symptoms caused by anoxemia, particularly cyanosis and dyspnea.

Sometimes patients who presented with pulmonary edema due to gas poisoning were treated in oxygen chambers, which could be supplied with 40-60 percent oxygen. These chambers were found to be effective in treating cases of chronic gas poisoning. Some patients would spend up to 16 hours a day inside one with good results. (3, page 360)

However, this therapy wasn't practical for common use.

Another means of providing these patients oxygen was to use a tube or funnel to aim the oxygen at their faces, although studies showed this provided no more than a 2 percent increase in oxygenation of inspired air.

So this opened the door for an improved oxygenation apparatus that was easily portable by medics, comfortable to wear, could be used long term for chronic cases, and provided a therapeutic dose of oxygen. John Haldane invented such a device, and it was called the "Haldane Apparatus." (3, page 370)

Alvin Barach said Haldane's apparatus provided oxygen blended into the air the patient inspired, and by doing this the amount of oxygen making it to the alveoli was greatly increased. By this means, the patient was supplied with a therapeutic level of oxygen. (3, page 370)

Barach described the device as consisting of an oxygen tank, a reducing valve, and a face mask. He said: (3, page 370)

"The mask was connected with a connecting bag which received oxygen from the tank, and with the outside air, from which the patient breathed. Oxygen was added to the inspired air in amounts of from one to four liters per minute. This was largely used in acute cases with generally good results." (3, page 370)

The problem with the Haldane apparatus was the only patients who tolerated it were those who were comatose. It worked great for these patients. Yet for others, for those who were awake and alert, it was not comfortable. Patient's complained that having the mask over their faces created a feeling of claustrophobia, and the mask was also hot and stuffy. This was especially a problem on hot days. Some patients simply didn't tolerate the mask, and some even ripped it off, refusing to wear it. (3, page 370)

Another problem, a pretty severe one actually, was it was impossible for clinicians to see through the opaque rubber masks. Clinicians learned to be vigilant, although this sometimes didn't prevent them from getting busy and not recognizing a patient was vomiting or expectorating foaming pulmonary edema. When not recognized, secretions occluded airways resulting in worsening anoxemia.

This concern opened the door for a more comfortable and safer oxygenation device.

One such device was the nasal cannula or prongs devised by Captain Adrian Stokes, M.D., in 1917. Stokes created the device while triaging patients on the war front who were suffocating due to pulmonary edema, and to which the tight fitting rubber mask of Dr. Haldane was not feasible. The metal cannula provided less oxygen than Haldane's device, although it helped medics keep pulmonary fluid from re-entering and blocking the airway. (1, page 38) (3, page 370) (5, page 8) (6)

Stoke's cannula was a device similar in design to what we use today, although it was supplied by rubber tubing and the prongs were made of metal, and therefore was not very comfortable. However, patients tolerated it much better than the rubber mask, and of course it was safer. (1, page 38) (3, page 370) (5, page 8) (6)

A similar device was the rubber nasal catheter, which was initially invented by Arbuthnot Lane in 1907, although re-introduced by Stokes in 1917. The catheter was introduced into the United States in 1931 by Waters and Wineland. (1, page 17) (5, pages 8-9) (7, page 20)

The soft, rubber catheter (later made of pliable plastic) was a 12 inch long tube that was blindly inserted into one of the nostrils and then secured to the forehead. The patient would then open his mouth, depress his tongue to the bottom of his mouth, and the physician or nurse would check to see that the catheter was in place at the back of the airway. (4)

The end that remained outside the patient had a fitting to which oxygen supply tubing was connected. On the distal side of the catheter, the side inside the patient's airway, were a series of small holes to allow oxygen to enter the patient's airway. (4)

Catheters were designed for adults and pediatrics, the flow was set at 1- 5 lpm, and the the delivered oxygen was 22-35%. The catheters would stay in the nose for a day or two. If it was needed longer a new catheter had to be inserted. (4)

Most experts recommended changing the catheter every 24 hours to prevent tissue breakdown, and most hospital protocols eventually called for changing it every eight hours.

So you can see that while it was more convenient for the patient, there was some risk to the patient too. It also provided some inconvenience for those taking care of patients requiring it.

While nasal catheters were simple to insert and manage, and while they were generally well accepted by patients, they did not provide enough oxygen in patients presenting with acute pulmonary edema or worsening pneumonia to eliminate cyanosis. (3, page 370)

The nasal catheter was the most commonly used device for supplying supplemental oxygen prior to the invention of the modern nasal cannula in the 1960s.

Figure 2 --Apparatus for givingoxygen.(3, page 374)

Another option was a device similar to the one in figure 2. The apparatus works this way:

"The patient breathes through the rubber mouthpiece M (or a mask could be used) through the can of soda-lime C into a rebreathing bag B. The carbon dioxide exhaled is removed by the soda-lime, and oxygen is admitted from the tank O at a sufficient rate to keep B inflated.In this way the patient rebreathes pure oxygenfrom the apparatus,but since his nose is left open he dilutes this with a certain proportion of atmospheric air. In practice this results in the inhalation of from 40 to 60 per cent, oxygen." (3, page 374)

Yet another option was the oxygen tent. These were clear canopies that were made to cover the entire bed. A machine at the bedside provided an environment inside the tent of about 30 percent oxygen. These were effective as far as oxygenating some patients, although the original oxygen tents were hot and stuffy, and this particularly posed a problem on hot days.

Patients would generally go inside one long enough to catch their breath, and then they'd return to breathing room air. (1, page 94)

Barach recommended to physicians that the best means of measuring oxygenation status was by monitoring the heart rate, respiratory rate, and especially the level of cyanosis (bluish skin color). This was much more logical than an invasive blood draw. (3, page 370)

Caregivers would ultimately learn to monitor these signs, along with level of consciousness, before, during and after therapy. This, they found, was the best means of monitoring the effectiveness of oxygenation therapy, and whether or not it was still needed. (2)

What equipment to use to supply oxygen depended on what equipment was available, the physician taking care of the patient, and the independent oxygenation requirements of patient.

How long oxygen therapy was used primarily depended on the patient and how quickly, or slowly, the underlying condition resolved. (2)

Still, by 1922, when Barach wrote many of his papers, he explained that...

"the use of oxygen in medical therapy occupies at present an uncertain role."

Despite Barach's doubts, the 1920s was an oxygen revolution of sorts.

Barach would go on to study the effects of oxygen therapy on a variety of respiratory diseases, including pneumonia and cor pulmonale. He would also study the effects of oxygen therapy on respiratory failure. For his work, he is often considered the father of modern oxygen therapy.

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John Bottrell is a respiratory therapist. He's a featured asthma and COPD writer for asthma.net and copd.net. He's the creator and occasionally writer for Respiratory Therapy Cave, the #1 respiratory therapy blog. He's an avid historian and creator of Asthma History. His blog posts have been featured in various newspapers, such as the Chicago Tribune. He has previously been a featured asthma/COPD writer for Healthcentral.com and asthma writer for Answers.com.